Acromegaly overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Acromegaly (from Greek akros "extreme" or "extremities" and megalos "large" - extremities enlargement) is a hormonal disorder that results from too much growth hormone in the body. The pituitary gland, a small gland in the brain, makes growth hormone. In acromegaly, the pituitary produces excessive amounts of growth hormone, usually from a benign, or noncancerous, tumor on the pituitary gland. These benign tumors are called pituitary adenomas.
Acromegaly most commonly affects middle-aged adults and can result in serious illness and premature death. Because of its insidious onset and slow progression, the disease is hard to diagnose in the early stages and is frequently missed for many years. Common symptoms include slow enlargement of jaw, hands, feet, and coarsening of facial features. The most serious health consequences of acromegaly are type 2 diabetes, high blood pressure, increased risk of cardiovascular disease, and arthritis. Patients with acromegaly are also at increased risk for colon polyps, which may develop into colon cancer if not removed.
When growth hormone-producing adenomas occur in childhood, the disease that results is called gigantism rather than acromegaly. A child’s height is determined by the length of the so-called long bones in the legs. In response to growth hormone, these bones grow in length at the growth plates—areas near either end of the bone. Prior to puberty, excessive growth hormone exposure causes increased height. Growth plates fuse after puberty, so the excessive growth hormone production in adults does not affect height.
Historical Perspective
Acromegaly was first described by DR. Johannes Wier in 1567. Dr. Verga reported a case of acromegaly in 1864 and it was a case of a patient with a disproportionate big face. Through 1877 to 1900s, many physicians reported cases of acromegaly. In 1970, Dr. Besser used bromocriptine in the treatment of acromegaly and it showed a remarkable improvement in the patients. In 1988, FDA approved for the octreotide as a treatment to acromegaly.
Classification
There is no classification system established for acromegaly
Pathophysiology
Acromegaly is caused by prolonged overproduction of growth hormone by the pituitary gland. Growth hormone is part of a cascade of hormones that, as the name implies, regulates the physical growth of the body. This cascade begins in a part of the brain called the hypothalamus, which makes hormones that regulate the pituitary. One of the hormones in the GH axis is growth hormone-releasing hormone (GHRH), which stimulates the pituitary gland to produce GH.
Secretion of GH by the pituitary into the bloodstream stimulates the liver to produce another hormone called insulin-like growth factor I (IGF-I). IGF-I is what actually causes tissue growth in the body. High levels of IGF-I, in turn, signal the pituitary to reduce GH production.
The hypothalamus makes another hormone called somatostatin, which inhibits GH production and release. Normally, GHRH, somatostatin, GH, and IGF-I levels in the body are tightly regulated by each other and by sleep, exercise, stress, food intake, and blood sugar levels. If the pituitary continues to make GH independent of the normal regulatory mechanisms, the level of IGF-I continues to rise, leading to bone overgrowth and organ enlargement. High levels of IGF-I also cause changes in glucose (sugar) and lipid (fat) metabolism and can lead to diabetes, high blood pressure, and heart disease.
Causes
Common causes of acromegaly include pituitary adenoma and acidophil stem cell adenomas. Less common causes of acromegaly include GHRHsecreting tumors as hypothalamic tumors, small cell lung cancer, adrenal adenoma, and pheochromocytoma. Other causes include GH secreting tumors as lymphoma and pancreatic islet cell tumor.
Differentiating Acromegaly overview from Other Diseases
Acromegaly must be differentiated from other diseases that cause acral features like skin thickening and linear bone growth. These diseases such asMarfan syndrome, precocious puberty, prolactinoma, and pachydermoperiostosis.
Epidemiology and Demographics
The prevalence of acromegaly is estimated to be 2.8 - 13.7 per 100.000 individuals worldwide. In the United States, the incidence of acromegaly is 0.11 per 100,000 indviduals. Acromegaly affects men and women equally.
Risk Factors
Common risk factors in the development of acromegaly are the risk factors for pituitary adenoma development. These risk factors include a family history ofpituitary adenoma, MacCun Albright syndrome, lung cancers and adrenal tumors. Other risk factors include early menopause in females and young age females at the first childbirth.
Screening
According to the endocrine society, screening for acromegaly is recommended among patients with clinical features of acromegaly. These features include enlarged hands and feet, frontal protrusion, and skin thickening. The screening is performed by measurement of the IGF-1.